During a recent interview with Stephen Colbert at the Montclair Film Festival, Jon Stewart revealed that Hugh Grant was the worst guest he has ever had on "The Daily Show." “And we have had dictators on,” Stewart added, saying Grant will never be invited back. “He’s giving everyone [expletive] the whole time, and he’s a big pain in the [expletive].” And when Stewart aired a clip from Grant’s latest movie during his last appearance, the actor responded, “What is that clip? It’s a terrible clip.” Stewart parried, “Well, then make a better [expletive] movie.”

Even before his talk show aired on CNN, Piers Morgan announced that he would ban certain guests, beginning with Madonna. Morgan later upped the stakes by tweeting that she wasn’t welcome on his U.K. talk show either. Also on the banned list is Heather Mills, whom Morgan regrets introducing to Paul McCartney (“I realized I'd pushed one of the world's great golddiggers in the direction of one of my heroes," he told "The Hollywood Reporter." and Keith Olbermann—“just because it would really annoy him."

As retaliation for Piers Morgan banning her friend Madonna from his CNN show, Rosie O’Donnell told "Access Hollywood" that Morgan would be the one celebrity not allowed on her talk show on OWN: “Only because he banned Madonna for no real reason when his show started.” By the next year, however, the two had made up from their mock feud, and O’Donnell even guest hosted Morgan’s program.

Comedian Kathy Griffin has made a sport out of getting banned from talk shows. She has famously been blacklisted by "The View" several times for talking about Barbara Walters and the other co-hosts in her act, and was banned by David Letterman for cursing too much on his show in the 90s. But earlier this year, Letterman lifted his ban and had Griffin on as a guest. Rather than play it safe, Griffin tried to take off her dress on the show—and wasn’t wearing underwear.

When Gilbert Gottfried made an appearance on a rival radio show, Howard Stern banned the comedian from his program—by inviting him on to talk about it. At length. “Oh OK,” Gottfried laughed when told he was banned, “I won’t come on.” But years later, when Gottfried was fired for tweeting jokes about the Japanese tsunami, Stern came to his defense. “When the Aflac people hired him to be the duck, they knew... his humor is offensive,” Stern said on his show. “There’s no reason for him to be fired. But to be fired for offensiveness... he should never have been hired then.”

After being named permanent guest host of "The Tonight Show with Johnny Carson" in 1983, Joan Rivers committed the ultimate show business sin three years later when she left start her own late-night talk show on Fox and didn’t tell Carson first. Rivers’s new show was soon cancelled, and she never appeared on Carson’s couch again—a ban that Jay Leno has honored during the years he has hosted the show. And the comedian still feels the sting. Three years ago, during an interview with MSNBC, Rivers called Carson a “nasty man."